This invention is directed to a dental syringe and carpule, of the type used to administer a local anesthetic or other medication to a dental patient. The carpule, containing anesthetic, for example, is inserted into the barrel of the syringe, and a needle on the distal end of the syringe pierces a puncturable seal on the carpule. The plunger of the syringe contacts a rubber or rubber-like piston that can be pushed forward to eject the anesthetic solution into the patient's gum or jaw.
In most current syringes, the plunger has a barbed member, i.e., a “harpoon” at its distal end and the harpoon pierces and engages the piston. This permits the dental practitioner to pull back on the plunger to withdraw the piston proximally, which causes the syringe to aspirate, i.e., to draw fluids back in through the needle. In order to remove the carpule from the barrel of the syringe, the dentist pulls back on the plunger to withdraw the plunger from the carpule. However, it frequently occurs that the harpoon fails to disengage from the piston or plug, and the piston is pulled out from the proximal end of the tube of the carpule.